CEMS and XPS studies on iron states in sputtered Fe-Al-O granular TMR films

摘要

In order to glean the origin of the difference between TMR effects in sputtered Fe-Al-O granular films and Fe-implanted Al_2O_3 granular film, the iron ionic states and the size distributions for α-Fe particles in sputtered Fe-Al-O granular TMR films were investigated using Conversion Electron Moessbauer Spectros-copy (CEMS) with and without applied magnetic field. From CEMS without magnetic field, the ferric iron phase (Fe~(3+)) in contrast to the superparamagnetic α-Fe particles and ferrous iron(Fe~(2+)) phases observed for the Fe- implanted samples, was found to appear in the sputtered films where TMR effect was noticeable. From CEMS applied with 0.4 T magnetic field, the size distribution of α-Fe superparamagnetic particles was found to be broaden around 4 nm and not separated into two groups as observed in the Fe-implanted Al_2O_3 granular film. In addition XPS was used for depth profiling.